This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The body's response to an infectious or non-infectious insult has been termed the systemic inflammatory response syndrome (SIRS). When this process is known to be caused by an infectious agent, the terms sepsis and SIRS are synonymous. SIRS/sepsis and its sequelae, including Acute Lung Injury, remain a leading cause of morbidity and mortality in children. Based on new insights into the molecular processes of SIRS, we hypothesize that in children with SIRS, the progression to septic shock, MODS, and/or death, is associated with the variable expression patterns of platelet granzymes. Specific Aim 1: Development of a genomic database of children with SIRS, septic shock, and/or MODS and healthy controls. In order to test our central hypothesis, it will be necessary to establish a genetic and clinical database of 22 individuals to account for the anticipated diversity of host responses to SIRS. We propose to isolate cell fractions from concurrent collections of peripheral whole blood from 22 children with SIRS recruited from the CNMC PICU. Two samples will be obtained from each SIRS participant;one will be obtained at the onset of SIRS and then the other sample 48 hours after that. DNA will also be isolated from the blood samples. SIRS participants will be recruited from the CNMC PICU. In addition, a single peripheral blood sample will be collected from 20 healthy normal control children enrolled in the CNMC ED. Specific Aim 2: Perform functional in vitro lymphocyte killing assays on platelets from all enrolled patients in Aim 1. We will classify our patients according to the proposed categories: 1) controls, 2) SIRS alone, 3) SIRS progressing to septic shock/MODS, and 4) SIRS progressing to septic shock/MODS and death. Using the in vitro lymphocyte killing assays, we will determine the degree of cytotoxicity of each participant's platelets. Cytotoxicity in each of the proposed categories will be compared in order to test our central hypothesis that the progression from SIRS to septic shock, MODS, and/or death is dependent on the expression patterns of platelet granzymes.